1. Technical Field
The present invention relates to a printing device used for a facsimile device, a copy machine, or an office automation (OA) device, a program for controlling a printing device, and a method of controlling a printing device. More particularly, the present invention relates to a printing device suitable for a so-called inkjet type printing process for ejecting a plurality of minute color particles of liquid ink onto printing paper (recording material) so as to form a predetermined character or image, a program for controlling a printing device, a method of controlling a printing device, a printing data creating device, a program for creating printing data, and a method of creating printing data.
2. Related Art
Hereinafter, a printing device, particularly, an inkjet type printer (hereinafter, referred to as ‘inkjet printer’) will be described.
Generally, since an inkjet printer is advantageous in that it is available at a low cost and a color printing material having a high quality can be easily obtained, it has been widely used for office and personal use as personal computers and digital cameras have become popular.
This inkjet printer generally has the following structure. A movable body called a carriage, in which an ink cartridge and a printing head are integrally formed, ejects minute particles of liquid ink in a dot shape through nozzles of the printing head on a printing medium (paper) while reciprocally moving on the recording medium in a direction vertical to a paper transporting direction, and a predetermined character or image is formed on the printing medium so as to create a desired printing material (an ink cartridge and a printing head may be separated from each other and ink may be supplied to the printing head through a tube or the like). In addition, the carriage includes ink cartridges of four colors (black, yellow, magenta, and cyan) including black and printing heads for the respective four colors, so that not only black-and-white printing but also full color printing combining the respective colors are easily performed (In addition, ink cartridges of six colors including the above-mentioned four colors, light cyan, and light magenta or seven colors or eight colors has been practically used).
As such, in the inkjet printer in which the printing is performed while reciprocally moving the printing head of the carriage on the recording medium in a direction vertical to a paper transporting direction, the printing head needs to perform a reciprocal motion several tens of times or several hundreds of times or more so as to clearly perform printing corresponding to one page. Therefore, it takes a lot of time for the inkjet printer to perform printing, as compared with another type of printing device, for example, a laser printer using an electrophotographic technology of a copy machine or the like.
In the meantime, in an inkjet printer in which a printing head having a length which is the same size (or larger) as a width of the printing paper is provided and a carriage is not used, since it is not necessary for the printing head to move in a width direction of the printing paper and the printing can be done through a so-called one scanning (one pass) process, high speed printing can be performed, similar to the laser printer. In addition, since it is not required to provide the carriage with the printing heads mounted thereon and a driving system moving it, a printer case can become smaller and lighter, and unwanted noise can be further reduced. The inkjet printer of the former is generally called a ‘multipass-type printer’ or a ‘serial printer’, and the inkjet printer of the latter is generally called a ‘line-head-type printer’.
In the printing head necessary for the inkjet printer, minute nozzles each having a diameter within a very small range of 10 to 70 μm are disposed in one row or a plurality of rows in a printing direction at predetermined intervals. As a result, an ink ejection direction of some nozzles may be inclined or the nozzle position may deviate from an ideal position due to manufacturing error, so that a landing position of some dots formed by the nozzles may deviate from an ideal position, thereby causing a so-called ‘flying curve phenomenon’ to occur. In addition, nozzles having a large variation, in which each nozzle may extremely increase or decrease an ink amount as compared with an ideal ink amount, may exist due to the variation characteristics of the nozzle.
As a result, a printing failure called a ‘banding (stripe) phenomenon’ may occur in a portion printed by using the defective nozzles, so that a printing quality may be lowered. Specifically, if the ‘flying curve’ phenomenon occurs, the distance between dots ejected by adjacent nozzles does not become uniform. As such, ‘white stripes’ (in a case in which the printing paper is white) occur in a portion where the distance between adjacent dots is larger than the normal (desired) distance, and ‘thick stripes’ occur in a portion where the distance between adjacent dots is smaller than the normal distance. In addition, in a case in which an ink amount is different from an ideal ink amount, thick stripes occur in dots formed by the nozzles ejecting a large amount of ink, and white stripes occur in dots formed by the nozzles ejecting a small amount of ink.
Specifically, it is likely for the banding phenomenon to occur more in ‘a line-head-type printer’ where the printing head or the printing medium is fixed (one pass printing) than in ‘the multipass-type printer’ (serial printer) (in the multipass-type printer, there is a technology in which the printing head performs a reciprocal motion many times to prevent the banding from occurring).
For this reason, in order to prevent the printing failure caused by ‘the banding phenomenon’, research and development have been performed in respect to the hardware, such as improving a manufacturing technology or design of the printing head. However, it is not yet possible to provide a perfect printing head capable of preventing the ‘banding phenomenon’ due to limitations imposed by manufacturing costs and current technology.
Accordingly, in addition to the improvement in the hardware, a technology, which reduces the banding phenomenon by using printing control, that is, a software-like method, which will be described in detail below, has been used.
For example, in JP-A-2002-19101 or JP-A-2003-136702, which will be described below, in order to resolve problems of the nozzle variation or non-ejection of the ink, the problem of the head variation is resolved by using a shading correction technology in a portion having the low printing concentration, and the problem of the banding or variation is resolved by using another color (for example, when being printed with black, cyan or magenta is used) in a portion that has the high printing concentration.
Further, in JP-A-2003-63043, which will be described below, a method has been suggested in which for a solid image (that is, a base is covered such that the base is not seen), an ink ejection amount of each nozzle adjacent to the non-ejection nozzle is increased and a solid image is formed using all of nozzles.
Furthermore, in JP-A-05-30361, a method is used in which a variation amount of each nozzle is fed back to an error spreader, so that the variation of the ink ejection amount of the nozzle is absorbed, thereby preventing a banding phenomenon from occurring.
However, according to the method of reducing the banding phenomenon or variation by using another color as in JP-A-2002-19101 or JP-A-2003-136702, since the color of the processed portion may be changed, it is not suitable for printing that requires high definition and high quality, as in color transfer image printing.
In addition, when a method of preventing ‘a white stripe phenomenon’ by distributing information of the non-ejection nozzle to the left and right sides with respect to a portion where the concentration is high is applied to the above-mentioned ‘flying curve phenomenon’, the white stripe can be reduced, but the banding may remain in the portion where the concentration is high.
In a method disclosed in JP-A-2003-63043, if the printing material is a solid image, the problem does not occur, but if the printing material is a printing material of a halftone, this method cannot be used. In addition, if the method of burying thin lines using another color is infrequently used, the problem does not occur. However, in an image in which another color is continuously generated, the color of the part of the image may be changed, similarly to the above-mentioned case.
Furthermore, in the method disclosed in JP-A-05-30361, with respect to the problem that the contents formed by the dots vary, the proper feedback process is complicated, and it is difficult to resolve it.